A man convicted of killing an Inglewood police officer is set to walk free and the officer's family spoke out, demanding the man remain in prison.

"I never thought we'd be here trying to fight for him to stay in prison. What kind of justice system would release a cop killer?" son George Aguilar Jr. said.

Veteran Inglewood Sgt. George Aguilar was gunned down while chasing several robbery suspects in March 1988. The mastermind behind the crime, Joevone Elster, was convicted and sentenced to life in prison.

But Aguilar's devastated family said they learned Tuesday afternoon that Elster is set to be released from prison on Friday.

"He absolutely loved his job. He gave his life for it, and now our justice system is going to allow the person responsible for his murder to walk the streets," daughter Camille Zamorano said.

They said Aguilar's killer was previously granted parole, but Gov. Jerry Brown reversed the decision. The governor's office said Los Angeles Superior Court then overturned his reversal, allowing the original parole grant to be reinstated.

"It was a nightmare for all of us and it never has ended. There should be a law that anybody that kills a police officer should never see the outside of prison walls," brother Larry Aguilar said.

Aguilar's family is again pleading for the governor's help and asking the public to speak out. The father of four was well-known in the law enforcement community. His murder was even turned into a docudrama with Danny Trejo playing the veteran officer.

His family said they cannot believe the killer will soon walk free.

"My dad lost his life when he was 46 years old. Now here we are, the man responsible for my dad's death - his life is about to begin at just about the same age. Where is the fairness in that?" George Aguilar Jr. said.

The governor's office said Brown is not likely to overturn the court's decision because it has already gone to the courts and usually it does not succeed in reversing a reversal that has already been approved by that court.

Aguilar's family said they will continue to fight to keep his killer in prison.